Hopes for PCOS cure as scientists reveal cause in mice

Polycystic ovary syndrome (PCOS) may be due to a hormone imbalance before birth, research has revealed. 

The disease may be triggered before birth by excessive exposure to anti-MÏ‹llerian hormone (AMH) in the womb, researchers found. They were then able to counter the symptoms of the syndrome in mice. A clinical trial to see if the treatment works in women will begin later this year.

In the study in Nature Medicine, Dr Paolo Giacobini at the French National Institute of Health and Medical Research (Inserm), and his team discovered that pregnant women with PCOS have 30 percent higher levels of AMH than usual. As the disease can be hereditary, the researchers then investigated whether the high levels of hormone could induce the same condition in female offspring.

To do this, scientists injected AMH into pregnant mice and found that their offspring developed symptoms which mirrored those observed in women with PCOS, including infrequent ovulation and delays in becoming pregnant. The authors surmised that the excess hormone resulted in overstimulation of a subset of neurons leading to increased levels of testosterone. 

Using the IVF drug cetrorelix to control hormone levels, the researchers were able to reverse the induced symptoms of PCOS in mice. By the end of the year, the team hopes to trial cetrorelix for women with PCOS.

'It could be an attractive strategy to restore ovulation and eventually increase the pregnancy rate in these women,' said Dr Giacobini.

PCOS is estimated to affect between 8 and 20 percent of women. Symptoms of the condition include high levels of testosterone resulting in excessive hair growth and acne, and irregular periods often leading to difficulties conceiving. Despite being a common disorder, the underlying cause has been poorly understood. 

'It's by far the most common hormonal condition affecting women of reproductive age, but it hasn't received a lot of attention,' Professor Robert Norman of the University of Adelaide in Australia, who was not involved in the study, told New Scientist.

The study presents 'a radical new way of thinking about polycystic ovary syndrome and opens up a whole range of opportunities for further investigation', he concluded.